The use of ultrasonic instruments in surgical applications is well known. One widely used type of instrument is an ultrasonic hand piece that is used in ophthalmic applications, such as in the removal of cataracts from the eye by phacoemulsification.
FIG. 6 depicts one such type of prior art ultrasonic hand piece as shown in U.S. Pat. No. 4,504,264 of Kelman. This hand piece has a housing 10 of, for example, plastic or metal, within which is supported a transducer means 11 for generating mechanical vibrations upon excitation with an alternating-current electrical signal. The transducer 11 is shown as a magnetostrictive transducer with an electrical coil 12 wound about each leg of a stack of metal laminations so that longitudinal mechanical vibrations are produced. The transducer can also be of the piezoelectric type. There is a connecting body 16 of, for example, titanium, having a reduced diameter distal end portion, which also can be an attached separate portion. The connecting body forms an acoustic impedance transformer for conveying the longitudinal vibrations of the transducer 11 for application to an operative tool or working tip 14 connected to the distal end of the connecting body 16.
The work tip 14 is at least partially external of the housing 10. It is connected, such as by a screw thread, to the narrowed distal end of the connecting body 16 so as to be coupled to the transducer 11 so as to be longitudinally vibrated thereby. The working tip 14 is an elongated, hollow tip of a suitable metal, such as titanium, that is capable of supporting ultrasonic vibrations. It has a distal end of a desired shape to be placed against the tissue to be removed. The work tip 14 has a base portion 15 in threaded engagement with the distal end of the connecting body 16. The tip 14 can be interchanged by use of the screw threads.
The distal end of the tip 14 is shown surrounded by a sleeve 17, which may be made of a material such as silicone, whose proximal end 18 is supported in threaded engagement on a reduced diameter end of the housing 10. If desired, the proximal end of sleeve 17 can be engaged more proximally along the length of the housing 10. The connecting body 16 has two elastomeric 0-rings 19, 20 on its outer surface. These provide a fluid-tight seal between the connecting body 16 and the transducer means 11. A plurality of screws 51 are shown disposed around the axis of the housing 10 for preventing longitudinal displacement (other than vibration) or rotational movement of the vibratory structure within the housing and also for radial centering of the vibratory structure within the housing. Other types of conventional mounting arrangements can be used.
The hand piece also illustratively has electrical input terminals 40, 41 for applying a suitable electrical signal to the magnetostrictive transducer 11. Cooling water is shown provided inside the housing 10 from an inlet 42 to an outlet 43 and within a chamber between 0-ring 19 and a grommet 50 for circulation around the transducer and connecting body. This is not always necessary and is not used in most present day hand pieces.
The sleeve 17 around the tip 14 forms a first fluid passage 21 between the tip 14 and the sleeve for irrigation fluid. An inlet 22 is provided on the housing or sleeve distally of the 0-ring 20 for supplying the irrigation fluid to the passage 21 from a fluid supply, e.g., a bag of saline solution (not shown).
A passage 23 is formed through the connecting body 16 that is in communication with a central passage 25 of the work tip 14. An outlet 24 on the housing or sleeve receives a suction (aspiration) force that is applied to the passage 23 in the connecting body and the central passage 25 in the work tip. A chamber 31 is formed between the spaced 0-rings 19, 20 on the body 16 and the housing 10, with which the aspiration force from outline 24 communicates. Thus the aspiration force is from the source (e.g., a suction pump not shown), into the chamber 31 between the 0-rings, through the passage 23 in the connecting body and the passage 25 in the work tip 14. Tissue that is emulsified by the work tip is aspirated from the operating site by the aspiration flow force. In particular, saline solution introduced into the eye through fluid passage 21 and tissue displaced by the vibration force of the tip 14, is drawn into the distal end of passage 25 and passes out of the hand piece through outlet 24. It should be noted that passage 25 is located concentrically within passage 21.
As indicated, other apparatus (not shown) for use with the hand piece include the suction pump for producing the aspiration fluid (suction), the treatment fluid supply (irrigation fluid, such as a saline liquid), an oscillator for applying an electrical signal to the vibratory structure and control apparatus therefore. All of these are of conventional construction.
Considering now the operation of the hand piece of FIG. 6. When an electrical signal having a frequency of, for example, 40,000 cycles/second is applied to the coil 12 around the magnetostrictive transducer 11, the transducer 11 vibrates longitudinally at 40,000 cycles per second, thereby vibrating the connecting bodies 13, 16 and the work tip 14. Treatment fluid is supplied through inlet 22 and fluid passage 21 to bathe the tissue in the operating site region around the working tip 14. Suction force is applied through inlet 24 and passage 23 to the working tip 14 passage 25 to withdraw the tissue fragmented by the work tip along with some of the treatment fluid.
Instruments of the type described above are often used in cataract surgery in which the eye lens is removed from the eye capsule and an intra-ocular lens (IOL) is then implanted. In such a procedure before the IOL is implanted it has been found to be desirable to cleanup lens substance and lens epithelial cells (LEC's) in the capsular bag and to remove them. Doing this procedure provides a more stable and long-term fixation for certain types of IOL's in the capsular bag. One manner of accomplishing the cleanup is to use a combination of irrigation of the capsular bag interior with a liquid together with the application of low power ultrasonic energy. This dislodges the unwanted cells and substances so that they can be removed from the capsular bag by the aspiration fluid flow.
In a cleanup procedure it is advantageous if the flow of the irrigation liquid can be made more directional than would be possible using the hand piece with the outer sleeve through which the liquid flows and exits from around the work tip that produces the ultrasonic energy. It is also better if the aspiration force is lower. As a result, typically a different tip from the one illustrated in FIG. 6, which breaks up the tissue, is used for the cleanup. Thus, the surgeon must remove the first work tip and place a new work tip in the eye. This second insertion into the eye increases the possibilities of infection and trauma. In an alternative prior art embodiment it is possible to use a separate lumen or probe that conveys only the irrigation liquid and a separate probe with a work tip. However, this has a disadvantage in that the surgeon would have to keep inserting and withdrawing the ultrasonic work tip and irrigation probe from the eye. As a result, this would also subject the patient to the increased possibilities of infection and trauma.
As shown in the present inventor's own U.S. Pat. No. 7,083,589, the surgical instrument may be provided with a coupler body located between the connecting body and the work tip. In such a case the aspiration fluid flow is provided from the work tip aspiration passage through the coupler to an outlet without coming into contact with the interior of the connecting body. Irrigation fluid can be provided through a portion of the housing that surrounds the proximal part of the work tip so as to form a chamber which is in communication with a separate passage in the work tip. The coupler is detachably connected to the connecting body. This allows the removal of the work tip, which becomes a single use part, so that the rest of the instrument can be reused by replacing the work tip without having to sterilize the connecting body. However, the portion of the housing surrounding the work tip and which forms the chamber for irrigation fluid, also needs to be replaced in this design.
Accordingly a need exists for a surgical hand piece that can provide both ultrasonic energy to emulsify tissue, cells and other substances which are aspirated by an aspiration fluid and an irrigation liquid that can be applied to part of the operating site being cleaned in a more directional and controlled manner. Further, it would be beneficial if the work tip were made replaceable in a more convenient manner, e.g., without having to replace part of the housing.